Lenalidomide intermediate preparation method

The present invention provides a lenalidomide intermediate preparation method, namely a preparation process of important intermediate 2-bromomethyl-3-nitro-methyl benzoate of 3-(4-amino-1-oxo-1,3-dihydro- 2H- isoindolyl-2-yl) piperidine-2,6-dione (namely lenalidomide).